JSFiddle - React, Tailwind, and code Playground

HTML

<div class="square blue selected"></div>
<div class="siquare orange"></div>
<div class="square red"></div>

CSS

body {
  background: black;
}
.square {
  width: 42px;
  height: 42px;
  display: inline-block;
  margin: 5px;
  background: linear-gradient(to bottom, transparent 0, rgba(255, 255, 255, 0.3) 50%, transparent 51%);
}

.square.selected {
  outline: 2px white solid;
}

.square.blue {
  background-color: #3BAACF;
}

.square.orange {
  background-color: #EB922E;
}

.square.red {
  background-color: #93131C;
}